Embodiments relate to a light emitting device, a light emitting device package, and a lighting system using the same.
A light emitting device (LED) may be implemented by a p-n junction diode, which has the characteristic converting an electrical energy to a light energy, and may be formed by combining a Group III element and a Group V element of the periodic table. The LED may implement various colors by adjusting the composition ratio of a compound semiconductor.
When a forward bias voltage is applied to a p-n junction diode, an electron of an n-type layer is recombined with a hole of a p-type layer to emit an energy corresponding to an energy gap between a conduction band and a valence band. The energy is mainly emitted in the form of heat or light. When the energy is emitted in the form of light, the p-n junction diode becomes an LED.
For example, due to high thermal stability and wide band gap energy, a nitride semiconductor has been an object of high interest in the field of developing optical devices and high power electronic devices. In particular, blue LED, green LED, UV LED, etc. using a nitride semiconductor have been commercialized and are being widely used.
In a related art vertical type LED, an n-type electrode and a p-type electrode are formed at an upper portion and a lower portion of the vertical type LED, respectively, for current injection. At this time, light emitted from a layer below the n-type electrode is absorbed into or reflected by the n-type electrode, and thus light emitting efficiency may decrease. Also, the light reflected by the n-type electrode is reabsorbed, and thus heat may be generated.
Further, according to the related art, the lifetime and reliability of the LED may be lowered due to current crowding.